1. Field of the Invention
The present invention relates to a microphone array system. In particular, the present invention relates to a system that performs various kinds of signal processing with respect to sound signals received at each microphone to provide various functions.
2. Description of the Prior Art
Hereinafter, a sound signal processing technique that utilizes a conventional technique will be described.
In the case where a plurality of sound sources of a desired signal and noise are present in a sound field, high quality enhancement of the desired sound, detection of the direction of the desired sound and noise suppression are important issues to be addressed for sound signal processing. Possible applications that utilize sound signal processing are in a wide range, such as animation and sound recording, systems for voice memo, hand-free telephones, teleconference systems, guest-reception systems or the like. In order to realize processing for enhancing a desired signal, suppressing noise and detecting the direction of the sound source, various sound signal processing techniques are under development.
Conventionally, microphones suitable for a particular application are used to obtain input sound signals for use in the processing for enhancing a desired signal, suppressing noise and detecting the direction of the sound source. For a compact video camera, a stereo microphone of MS (mid-side) system is widely used. In recent years, a unidirectional microphone is used in a personal computer that utilizes sound input in application software such as a voice memo, so that a suitable and articulate input sound signal can be obtained. Although these microphone are suitably used in view of the use and the cost, they are intended for a single use so that the directivity or the use is predetermined. Moreover, the processing of the sound signals received at the microphones is limited to the sound signal processing required by the application.
In an apparatus such as a conventional video camera or sound-inputtable personal computer that requires microphones suitable to each application and implements only sound signal processing required by the application that currently runs, the microphone and the sound signal processing function are each intended for a single function. However, for the apparatus designed to have a large number of functions, more flexible directionally received sound processing, sound source direction detecting processing and noise suppressing processing are desirable, and a function that has not conventionally required may be required in an application. In this case, since the configuration of the apparatus using the conventional microphone with a single function cannot meet this need, it is necessary to replace the microphone by a microphone suitable to the required function and also to replace the sound signal processing part for received sound signals by another one having the required function.
As the utilization system is varied, combining a plurality of kinds of sound signal processing such as directionally received sound processing, sound source direction detecting processing, noise suppressing processing and the like may be needed. In this case, it is necessary to prepare a plurality of microphones, each of which has a single function, and to perform sound signal processing for each individual microphone, and then perform sound signal processing of the combined results from the plurality of microphones. Thus, this conventional system requires a large number of microphones, so that it results in a large-scale apparatus. Furthermore, it may be difficult to physically arrange the required number of microphones to perform a plurality of kinds of sound signal processing in the necessary directions.
Therefore, with the foregoing in mind, it is an object of the present invention to provide a microphone array system that eliminates the replacement of the microphones and the replacement of the sound signal processing parts, which are conventionally required, regardless of the variation of the application or the sound signal processing function. It is another object of the present invention to achieve a sound signal processing function performing a combination of various kinds of sound signal processing in the same microphone arrangement.
A microphone array system using a unit having a signal processing function such as a personal computer as the platform includes at least one microphone arranged along each axis direction; and a received sound signal processing part for performing signal processing of sound signals received at the plurality of microphones, having a directional sound signal calculating function for calculating a directional sound signal to an arbitrary direction based on the received sound signal with a unidirectivity or bidirectivity pattern along the axis direction, and further having at least one function of other sound signal processing functions at the same time. It is preferable that the other sound signal processing functions includes a sound source direction detecting function and a noise suppressing function.
This embodiment achieves a microphone array system including a plurality of microphones using a personal computer and allows the system to have a plurality of sound signal processing functions including the function for calculating a directional sound signal to an arbitrary direction, the sound source direction detecting function and the noise suppressing function based on the processing of sound signals received at the microphone array.
In one embodiment, the plurality of microphones are non-directional microphones, at least two non-directional microphones are arranged in a first axis direction, and at least two non-directional microphones are arranged in a second axis direction that is orthogonal to the first axis. This makes it possible that the received sound signal processing part has a function for calculating a directional sound signal to an arbitrary direction based on a unidirectional estimated sound signal to a positive direction on the first axis and a bidirectional estimated sound signal to positive and negative directions on the second axis. In another embodiment, the plurality of microphones are unidirectional microphones, a first unidirectional microphone is directed to a positive direction on a first axis, and second and third unidirectional microphones are directed to positive and negative directions on a second axis that is orthogonal to the first axis. This makes it possible that the received sound signal processing part has a function for calculating a directional sound signal to an arbitrary direction based on a unidirectional received sound signal to a positive direction on the first axis and a bidirectional received sound signal to positive and negative directions on the second axis. In still another embodiment, the plurality of microphones are at least one unidirectional microphone and at least one bidirectional microphone, the unidirectional microphone is directed to a first axis direction, and the bidirectional microphone is directed to a second axis direction that is orthogonal to the first axis direction. This makes it possible that the received sound signal processing part has a function for calculating a directional sound signal to an arbitrary direction based on a unidirectional received sound signal to a positive direction on the first axis and a bidirectional received sound signal to positive and negative directions on the second axis. Furthermore, it is possible that the received sound signal processing part has a sound source direction detecting function for detecting a sound source direction, using a power in each axis direction of a sound signal calculated by the directional sound signal calculating function and cross-correlation thereof.
The microphone array system of the present invention can have the function for calculating a directional sound signal to an arbitrary direction and further have sound signal processing functions such as the function for detecting a sound source direction and the function for suppressing noise based on a plurality of kinds of processing of sound signals received at the microphone array by providing a plurality of microphones on a personal computer, which is the platform, regardless of the application or the sound signal processing function.
The microphone array system of the present invention can have the function for calculating a directional sound signal to an arbitrary direction based on a unidirectional estimated sound signal to the positive direction of the first axis and a bidirectional estimated sound signal to the positive and negative directions of the second axis.
The microphone array system of the present invention can have the sound source direction detecting function for detecting the sound source direction using the powers of the sound signals on the axes that are calculated by the directional sound signal calculating function and the cross-correlation coefficient therebetween.